/brz/remove-bazaar

# Copyright (C) 2008, 2009 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Repostory formats using CHK inventories and groupcompress compression."""

import time

from bzrlib import (

    bzrdir,

    chk_map,

    chk_serializer,

    debug,

    errors,

    index as _mod_index,

    inventory,

    knit,

    osutils,

    pack,

    remote,

    repository,

    revision as _mod_revision,

    trace,

    ui,

    )

from bzrlib.btree_index import (

    BTreeGraphIndex,

    BTreeBuilder,

    )

from bzrlib.index import GraphIndex, GraphIndexBuilder

from bzrlib.groupcompress import (

    _GCGraphIndex,

    GroupCompressVersionedFiles,

    )

from bzrlib.repofmt.pack_repo import (

    Pack,

    NewPack,

    KnitPackRepository,

    PackRootCommitBuilder,

    RepositoryPackCollection,

    RepositoryFormatPack,

    Packer,

    )

class GCPack(NewPack):

    def __init__(self, pack_collection, upload_suffix='', file_mode=None):

        """Create a NewPack instance.

        :param pack_collection: A PackCollection into which this is being

            inserted.

        :param upload_suffix: An optional suffix to be given to any temporary

            files created during the pack creation. e.g '.autopack'

        :param file_mode: An optional file mode to create the new files with.

        """

        # replaced from NewPack to:

        # - change inventory reference list length to 1

        # - change texts reference lists to 1

        # TODO: patch this to be parameterised

        # The relative locations of the packs are constrained, but all are

        # passed in because the caller has them, so as to avoid object churn.

        index_builder_class = pack_collection._index_builder_class

        # from brisbane-core

        if pack_collection.chk_index is not None:

            chk_index = index_builder_class(reference_lists=0)

        else:

            chk_index = None

        Pack.__init__(self,

            # Revisions: parents list, no text compression.

            index_builder_class(reference_lists=1),

            # Inventory: We want to map compression only, but currently the

            # knit code hasn't been updated enough to understand that, so we

            # have a regular 2-list index giving parents and compression

            # source.

            index_builder_class(reference_lists=1),

            # Texts: compression and per file graph, for all fileids - so two

            # reference lists and two elements in the key tuple.

            index_builder_class(reference_lists=1, key_elements=2),

            # Signatures: Just blobs to store, no compression, no parents

            # listing.

            index_builder_class(reference_lists=0),

            # CHK based storage - just blobs, no compression or parents.

            chk_index=chk_index

            )

        self._pack_collection = pack_collection

        # When we make readonly indices, we need this.

        self.index_class = pack_collection._index_class

        # where should the new pack be opened

        self.upload_transport = pack_collection._upload_transport

        # where are indices written out to

        self.index_transport = pack_collection._index_transport

        # where is the pack renamed to when it is finished?

        self.pack_transport = pack_collection._pack_transport

        # What file mode to upload the pack and indices with.

        self._file_mode = file_mode

        # tracks the content written to the .pack file.

        self._hash = osutils.md5()

        # a four-tuple with the length in bytes of the indices, once the pack

        # is finalised. (rev, inv, text, sigs)

        self.index_sizes = None

        # How much data to cache when writing packs. Note that this is not

        # synchronised with reads, because it's not in the transport layer, so

        # is not safe unless the client knows it won't be reading from the pack

        # under creation.

        self._cache_limit = 0

        # the temporary pack file name.

        self.random_name = osutils.rand_chars(20) + upload_suffix

        # when was this pack started ?

        self.start_time = time.time()

        # open an output stream for the data added to the pack.

        self.write_stream = self.upload_transport.open_write_stream(

            self.random_name, mode=self._file_mode)

        if 'pack' in debug.debug_flags:

            trace.mutter('%s: create_pack: pack stream open: %s%s t+%6.3fs',

                time.ctime(), self.upload_transport.base, self.random_name,

                time.time() - self.start_time)

        # A list of byte sequences to be written to the new pack, and the

        # aggregate size of them.  Stored as a list rather than separate

        # variables so that the _write_data closure below can update them.

        self._buffer = [[], 0]

        # create a callable for adding data

        #

        # robertc says- this is a closure rather than a method on the object

        # so that the variables are locals, and faster than accessing object

        # members.

        def _write_data(bytes, flush=False, _buffer=self._buffer,

            _write=self.write_stream.write, _update=self._hash.update):

            _buffer[0].append(bytes)

            _buffer[1] += len(bytes)

            # buffer cap

            if _buffer[1] > self._cache_limit or flush:

                bytes = ''.join(_buffer[0])

                _write(bytes)

                _update(bytes)

                _buffer[:] = [[], 0]

        # expose this on self, for the occasion when clients want to add data.

        self._write_data = _write_data

        # a pack writer object to serialise pack records.

        self._writer = pack.ContainerWriter(self._write_data)

        self._writer.begin()

        # what state is the pack in? (open, finished, aborted)

        self._state = 'open'

    def _check_references(self):

        """Make sure our external references are present.

        Packs are allowed to have deltas whose base is not in the pack, but it

        must be present somewhere in this collection.  It is not allowed to

        have deltas based on a fallback repository.

        (See <https://bugs.launchpad.net/bzr/+bug/288751>)

        """

        # Groupcompress packs don't have any external references

class GCCHKPacker(Packer):

    """This class understand what it takes to collect a GCCHK repo."""

    def __init__(self, pack_collection, packs, suffix, revision_ids=None,

                 reload_func=None):

        super(GCCHKPacker, self).__init__(pack_collection, packs, suffix,

                                          revision_ids=revision_ids,

                                          reload_func=reload_func)

        self._pack_collection = pack_collection

        # ATM, We only support this for GCCHK repositories

        if pack_collection.chk_index is None:

            raise AssertionError('pack_collection.chk_index should not be None')

        self._gather_text_refs = False

        self._chk_id_roots = []

        self._chk_p_id_roots = []

        self._text_refs = None

        # set by .pack() if self.revision_ids is not None

        self.revision_keys = None

    def _get_progress_stream(self, source_vf, keys, message, pb):

        def pb_stream():

            substream = source_vf.get_record_stream(keys, 'groupcompress', True)

            for idx, record in enumerate(substream):

                if pb is not None:

                    pb.update(message, idx + 1, len(keys))

                yield record

        return pb_stream()

    def _get_filtered_inv_stream(self, source_vf, keys, message, pb=None):

        """Filter the texts of inventories, to find the chk pages."""

        total_keys = len(keys)

        def _filtered_inv_stream():

            id_roots_set = set()

            p_id_roots_set = set()

            stream = source_vf.get_record_stream(keys, 'groupcompress', True)

            for idx, record in enumerate(stream):

                bytes = record.get_bytes_as('fulltext')

                chk_inv = inventory.CHKInventory.deserialise(None, bytes,

                                                             record.key)

                if pb is not None:

                    pb.update('inv', idx, total_keys)

                key = chk_inv.id_to_entry.key()

                if key not in id_roots_set:

                    self._chk_id_roots.append(key)

                    id_roots_set.add(key)

                p_id_map = chk_inv.parent_id_basename_to_file_id

                if p_id_map is None:

                    raise AssertionError('Parent id -> file_id map not set')

                key = p_id_map.key()

                if key not in p_id_roots_set:

                    p_id_roots_set.add(key)

                    self._chk_p_id_roots.append(key)

                yield record

            # We have finished processing all of the inventory records, we

            # don't need these sets anymore

            id_roots_set.clear()

            p_id_roots_set.clear()

        return _filtered_inv_stream()

    def _get_chk_streams(self, source_vf, keys, pb=None):

        # We want to stream the keys from 'id_roots', and things they

        # reference, and then stream things from p_id_roots and things they

        # reference, and then any remaining keys that we didn't get to.

        # We also group referenced texts together, so if one root references a

        # text with prefix 'a', and another root references a node with prefix

        # 'a', we want to yield those nodes before we yield the nodes for 'b'

        # This keeps 'similar' nodes together.

        # Note: We probably actually want multiple streams here, to help the

        #       client understand that the different levels won't compress well

        #       against each other.

        #       Test the difference between using one Group per level, and

        #       using 1 Group per prefix. (so '' (root) would get a group, then

        #       all the references to search-key 'a' would get a group, etc.)

        total_keys = len(keys)

        remaining_keys = set(keys)

        counter = [0]

        if self._gather_text_refs:

            bytes_to_info = inventory.CHKInventory._bytes_to_utf8name_key

            self._text_refs = set()

        def _get_referenced_stream(root_keys, parse_leaf_nodes=False):

            cur_keys = root_keys

            while cur_keys:

                keys_by_search_prefix = {}

                remaining_keys.difference_update(cur_keys)

                next_keys = set()

                def handle_internal_node(node):

                    for prefix, value in node._items.iteritems():

                        # We don't want to request the same key twice, and we

                        # want to order it by the first time it is seen.

                        # Even further, we don't want to request a key which is

                        # not in this group of pack files (it should be in the

                        # repo, but it doesn't have to be in the group being

                        # packed.)

                        # TODO: consider how to treat externally referenced chk

                        #       pages as 'external_references' so that we

                        #       always fill them in for stacked branches

                        if value not in next_keys and value in remaining_keys:

                            keys_by_search_prefix.setdefault(prefix,

                                []).append(value)

                            next_keys.add(value)

                def handle_leaf_node(node):

                    # Store is None, because we know we have a LeafNode, and we

                    # just want its entries

                    for file_id, bytes in node.iteritems(None):

                        name_utf8, file_id, revision_id = bytes_to_info(bytes)

                        self._text_refs.add((file_id, revision_id))

                def next_stream():

                    stream = source_vf.get_record_stream(cur_keys,

                                                         'as-requested', True)

                    for record in stream:

                        bytes = record.get_bytes_as('fulltext')

                        # We don't care about search_key_func for this code,

                        # because we only care about external references.

                        node = chk_map._deserialise(bytes, record.key,

                                                    search_key_func=None)

                        common_base = node._search_prefix

                        if isinstance(node, chk_map.InternalNode):

                            handle_internal_node(node)

                        elif parse_leaf_nodes:

                            handle_leaf_node(node)

                        counter[0] += 1

                        if pb is not None:

                            pb.update('chk node', counter[0], total_keys)

                        yield record

                yield next_stream()

                # Double check that we won't be emitting any keys twice

                # If we get rid of the pre-calculation of all keys, we could

                # turn this around and do

                # next_keys.difference_update(seen_keys)

                # However, we also may have references to chk pages in another

                # pack file during autopack. We filter earlier, so we should no

                # longer need to do this

                # next_keys = next_keys.intersection(remaining_keys)

                cur_keys = []

                for prefix in sorted(keys_by_search_prefix):

                    cur_keys.extend(keys_by_search_prefix.pop(prefix))

        for stream in _get_referenced_stream(self._chk_id_roots,

                                             self._gather_text_refs):

            yield stream

        del self._chk_id_roots

        # while it isn't really possible for chk_id_roots to not be in the

        # local group of packs, it is possible that the tree shape has not

        # changed recently, so we need to filter _chk_p_id_roots by the

        # available keys

        chk_p_id_roots = [key for key in self._chk_p_id_roots

                          if key in remaining_keys]

        del self._chk_p_id_roots

        for stream in _get_referenced_stream(chk_p_id_roots, False):

            yield stream

        if remaining_keys:

            trace.mutter('There were %d keys in the chk index, %d of which'

                         ' were not referenced', total_keys,

                         len(remaining_keys))

            if self.revision_ids is None:

                stream = source_vf.get_record_stream(remaining_keys,

                                                     'unordered', True)

                yield stream

    def _build_vf(self, index_name, parents, delta, for_write=False):

        """Build a VersionedFiles instance on top of this group of packs."""

        index_name = index_name + '_index'

        index_to_pack = {}

        access = knit._DirectPackAccess(index_to_pack)

        if for_write:

            # Use new_pack

            if self.new_pack is None:

                raise AssertionError('No new pack has been set')

            index = getattr(self.new_pack, index_name)

            index_to_pack[index] = self.new_pack.access_tuple()

            index.set_optimize(for_size=True)

            access.set_writer(self.new_pack._writer, index,

                              self.new_pack.access_tuple())

            add_callback = index.add_nodes

        else:

            indices = []

            for pack in self.packs:

                sub_index = getattr(pack, index_name)

                index_to_pack[sub_index] = pack.access_tuple()

                indices.append(sub_index)

            index = _mod_index.CombinedGraphIndex(indices)

            add_callback = None

        vf = GroupCompressVersionedFiles(

            _GCGraphIndex(index,

                          add_callback=add_callback,

                          parents=parents,

                          is_locked=self._pack_collection.repo.is_locked),

            access=access,

            delta=delta)

        return vf

    def _build_vfs(self, index_name, parents, delta):

        """Build the source and target VersionedFiles."""

        source_vf = self._build_vf(index_name, parents,

                                   delta, for_write=False)

        target_vf = self._build_vf(index_name, parents,

                                   delta, for_write=True)

        return source_vf, target_vf

    def _copy_stream(self, source_vf, target_vf, keys, message, vf_to_stream,

                     pb_offset):

        trace.mutter('repacking %d %s', len(keys), message)

        self.pb.update('repacking %s' % (message,), pb_offset)

        child_pb = ui.ui_factory.nested_progress_bar()

        try:

            stream = vf_to_stream(source_vf, keys, message, child_pb)

            for _ in target_vf._insert_record_stream(stream,

                                                     random_id=True,

                                                     reuse_blocks=False):

                pass

        finally:

            child_pb.finished()

    def _copy_revision_texts(self):

        source_vf, target_vf = self._build_vfs('revision', True, False)

        if not self.revision_keys:

            # We are doing a full fetch, aka 'pack'

            self.revision_keys = source_vf.keys()

        self._copy_stream(source_vf, target_vf, self.revision_keys,

                          'revisions', self._get_progress_stream, 1)

    def _copy_inventory_texts(self):

        source_vf, target_vf = self._build_vfs('inventory', True, True)

        self._copy_stream(source_vf, target_vf, self.revision_keys,

                          'inventories', self._get_filtered_inv_stream, 2)

    def _copy_chk_texts(self):

        source_vf, target_vf = self._build_vfs('chk', False, False)

        # TODO: This is technically spurious... if it is a performance issue,

        #       remove it

        total_keys = source_vf.keys()

        trace.mutter('repacking chk: %d id_to_entry roots,'

                     ' %d p_id_map roots, %d total keys',

                     len(self._chk_id_roots), len(self._chk_p_id_roots),

                     len(total_keys))

        self.pb.update('repacking chk', 3)

        child_pb = ui.ui_factory.nested_progress_bar()

        try:

            for stream in self._get_chk_streams(source_vf, total_keys,

                                                pb=child_pb):

                for _ in target_vf._insert_record_stream(stream,

                                                         random_id=True,

                                                         reuse_blocks=False):

                    pass

        finally:

            child_pb.finished()

    def _copy_text_texts(self):

        source_vf, target_vf = self._build_vfs('text', True, True)

        # XXX: We don't walk the chk map to determine referenced (file_id,

        #      revision_id) keys.  We don't do it yet because you really need

        #      to filter out the ones that are present in the parents of the

        #      rev just before the ones you are copying, otherwise the filter

        #      is grabbing too many keys...

        text_keys = source_vf.keys()

        self._copy_stream(source_vf, target_vf, text_keys,

                          'text', self._get_progress_stream, 4)

    def _copy_signature_texts(self):

        source_vf, target_vf = self._build_vfs('signature', False, False)

        signature_keys = source_vf.keys()

        signature_keys.intersection(self.revision_keys)

        self._copy_stream(source_vf, target_vf, signature_keys,

                          'signatures', self._get_progress_stream, 5)

    def _create_pack_from_packs(self):

        self.pb.update('repacking', 0, 7)

        self.new_pack = self.open_pack()

        # Is this necessary for GC ?

        self.new_pack.set_write_cache_size(1024*1024)

        self._copy_revision_texts()

        self._copy_inventory_texts()

        self._copy_chk_texts()

        self._copy_text_texts()

        self._copy_signature_texts()

        self.new_pack._check_references()

        if not self._use_pack(self.new_pack):

            self.new_pack.abort()

            return None

        self.pb.update('finishing repack', 6, 7)

        self.new_pack.finish()

        self._pack_collection.allocate(self.new_pack)

        return self.new_pack

class GCCHKReconcilePacker(GCCHKPacker):

    """A packer which regenerates indices etc as it copies.

    This is used by ``bzr reconcile`` to cause parent text pointers to be

    regenerated.

    """

    def __init__(self, *args, **kwargs):

        super(GCCHKReconcilePacker, self).__init__(*args, **kwargs)

        self._data_changed = False

        self._gather_text_refs = True

    def _copy_inventory_texts(self):

        source_vf, target_vf = self._build_vfs('inventory', True, True)

        self._copy_stream(source_vf, target_vf, self.revision_keys,

                          'inventories', self._get_filtered_inv_stream, 2)

        if source_vf.keys() != self.revision_keys:

            self._data_changed = True

    def _copy_text_texts(self):

        """generate what texts we should have and then copy."""

        source_vf, target_vf = self._build_vfs('text', True, True)

        trace.mutter('repacking %d texts', len(self._text_refs))

        self.pb.update("repacking texts", 4)

        # we have three major tasks here:

        # 1) generate the ideal index

        repo = self._pack_collection.repo

        # We want the one we just wrote, so base it on self.new_pack

        revision_vf = self._build_vf('revision', True, False, for_write=True)

        ancestor_keys = revision_vf.get_parent_map(revision_vf.keys())

        # Strip keys back into revision_ids.

        ancestors = dict((k[0], tuple([p[0] for p in parents]))

                         for k, parents in ancestor_keys.iteritems())

        del ancestor_keys

        # TODO: _generate_text_key_index should be much cheaper to generate from

        #       a chk repository, rather than the current implementation

        ideal_index = repo._generate_text_key_index(None, ancestors)

        file_id_parent_map = source_vf.get_parent_map(self._text_refs)

        # 2) generate a keys list that contains all the entries that can

        #    be used as-is, with corrected parents.

        ok_keys = []

        new_parent_keys = {} # (key, parent_keys)

        discarded_keys = []

        NULL_REVISION = _mod_revision.NULL_REVISION

        for key in self._text_refs:

            # 0 - index

            # 1 - key

            # 2 - value

            # 3 - refs

            try:

                ideal_parents = tuple(ideal_index[key])

            except KeyError:

                discarded_keys.append(key)

                self._data_changed = True

            else:

                if ideal_parents == (NULL_REVISION,):

                    ideal_parents = ()

                source_parents = file_id_parent_map[key]

                if ideal_parents == source_parents:

                    # no change needed.

                    ok_keys.append(key)

                else:

                    # We need to change the parent graph, but we don't need to

                    # re-insert the text (since we don't pun the compression

                    # parent with the parents list)

                    self._data_changed = True

                    new_parent_keys[key] = ideal_parents

        # we're finished with some data.

        del ideal_index

        del file_id_parent_map

        # 3) bulk copy the data, updating records than need it

        def _update_parents_for_texts():

            stream = source_vf.get_record_stream(self._text_refs,

                'groupcompress', False)

            for record in stream:

                if record.key in new_parent_keys:

                    record.parents = new_parent_keys[record.key]

                yield record

        target_vf.insert_record_stream(_update_parents_for_texts())

    def _use_pack(self, new_pack):

        """Override _use_pack to check for reconcile having changed content."""

        return new_pack.data_inserted() and self._data_changed

class GCRepositoryPackCollection(RepositoryPackCollection):

    pack_factory = GCPack

    def _already_packed(self):

        """Is the collection already packed?"""

        # Always repack GC repositories for now

        return False

    def _execute_pack_operations(self, pack_operations,

                                 _packer_class=GCCHKPacker,

                                 reload_func=None):

        """Execute a series of pack operations.

        :param pack_operations: A list of [revision_count, packs_to_combine].

        :param _packer_class: The class of packer to use (default: Packer).

        :return: None.

        """

        # XXX: Copied across from RepositoryPackCollection simply because we

        #      want to override the _packer_class ... :(

        for revision_count, packs in pack_operations:

            # we may have no-ops from the setup logic

            if len(packs) == 0:

                continue

            packer = GCCHKPacker(self, packs, '.autopack',

                                 reload_func=reload_func)

            try:

                packer.pack()

            except errors.RetryWithNewPacks:

                # An exception is propagating out of this context, make sure

                # this packer has cleaned up. Packer() doesn't set its new_pack

                # state into the RepositoryPackCollection object, so we only

                # have access to it directly here.

                if packer.new_pack is not None:

                    packer.new_pack.abort()

                raise

            for pack in packs:

                self._remove_pack_from_memory(pack)

        # record the newly available packs and stop advertising the old

        # packs

        self._save_pack_names(clear_obsolete_packs=True)

        # Move the old packs out of the way now they are no longer referenced.

        for revision_count, packs in pack_operations:

            self._obsolete_packs(packs)

class CHKInventoryRepository(KnitPackRepository):

    """subclass of KnitPackRepository that uses CHK based inventories."""

    def __init__(self, _format, a_bzrdir, control_files, _commit_builder_class,

        _serializer):

        """Overridden to change pack collection class."""

        KnitPackRepository.__init__(self, _format, a_bzrdir, control_files,

            _commit_builder_class, _serializer)

        # and now replace everything it did :)

        index_transport = self._transport.clone('indices')

        self._pack_collection = GCRepositoryPackCollection(self,

            self._transport, index_transport,

            self._transport.clone('upload'),

            self._transport.clone('packs'),

            _format.index_builder_class,

            _format.index_class,

            use_chk_index=self._format.supports_chks,

            )

        self.inventories = GroupCompressVersionedFiles(

            _GCGraphIndex(self._pack_collection.inventory_index.combined_index,

                add_callback=self._pack_collection.inventory_index.add_callback,

                parents=True, is_locked=self.is_locked),

            access=self._pack_collection.inventory_index.data_access)

        self.revisions = GroupCompressVersionedFiles(

            _GCGraphIndex(self._pack_collection.revision_index.combined_index,

                add_callback=self._pack_collection.revision_index.add_callback,

                parents=True, is_locked=self.is_locked),

            access=self._pack_collection.revision_index.data_access,

            delta=False)

        self.signatures = GroupCompressVersionedFiles(

            _GCGraphIndex(self._pack_collection.signature_index.combined_index,

                add_callback=self._pack_collection.signature_index.add_callback,

                parents=False, is_locked=self.is_locked),

            access=self._pack_collection.signature_index.data_access,

            delta=False)

        self.texts = GroupCompressVersionedFiles(

            _GCGraphIndex(self._pack_collection.text_index.combined_index,

                add_callback=self._pack_collection.text_index.add_callback,

                parents=True, is_locked=self.is_locked),

            access=self._pack_collection.text_index.data_access)

        # No parents, individual CHK pages don't have specific ancestry

        self.chk_bytes = GroupCompressVersionedFiles(

            _GCGraphIndex(self._pack_collection.chk_index.combined_index,

                add_callback=self._pack_collection.chk_index.add_callback,

                parents=False, is_locked=self.is_locked),

            access=self._pack_collection.chk_index.data_access)

        # True when the repository object is 'write locked' (as opposed to the

        # physical lock only taken out around changes to the pack-names list.)

        # Another way to represent this would be a decorator around the control

        # files object that presents logical locks as physical ones - if this

        # gets ugly consider that alternative design. RBC 20071011

        self._write_lock_count = 0

        self._transaction = None

        # for tests

        self._reconcile_does_inventory_gc = True

        self._reconcile_fixes_text_parents = True

        self._reconcile_backsup_inventory = False

    def _add_inventory_checked(self, revision_id, inv, parents):

        """Add inv to the repository after checking the inputs.

        This function can be overridden to allow different inventory styles.

        :seealso: add_inventory, for the contract.

        """

        # make inventory

        serializer = self._format._serializer

        result = inventory.CHKInventory.from_inventory(self.chk_bytes, inv,

            maximum_size=serializer.maximum_size,

            search_key_name=serializer.search_key_name)

        inv_lines = result.to_lines()

        return self._inventory_add_lines(revision_id, parents,

            inv_lines, check_content=False)

    def add_inventory_by_delta(self, basis_revision_id, delta, new_revision_id,

                               parents, basis_inv=None, propagate_caches=False):

        """Add a new inventory expressed as a delta against another revision.

        :param basis_revision_id: The inventory id the delta was created

            against.

        :param delta: The inventory delta (see Inventory.apply_delta for

            details).

        :param new_revision_id: The revision id that the inventory is being

            added for.

        :param parents: The revision ids of the parents that revision_id is

            known to have and are in the repository already. These are supplied

            for repositories that depend on the inventory graph for revision

            graph access, as well as for those that pun ancestry with delta

            compression.

        :param basis_inv: The basis inventory if it is already known,

            otherwise None.

        :param propagate_caches: If True, the caches for this inventory are

          copied to and updated for the result if possible.

        :returns: (validator, new_inv)

            The validator(which is a sha1 digest, though what is sha'd is

            repository format specific) of the serialized inventory, and the

            resulting inventory.

        """

        if basis_revision_id == _mod_revision.NULL_REVISION:

            return KnitPackRepository.add_inventory_by_delta(self,

                basis_revision_id, delta, new_revision_id, parents)

        if not self.is_in_write_group():

            raise AssertionError("%r not in write group" % (self,))

        _mod_revision.check_not_reserved_id(new_revision_id)

        basis_tree = self.revision_tree(basis_revision_id)

        basis_tree.lock_read()

        try:

            if basis_inv is None:

                basis_inv = basis_tree.inventory

            result = basis_inv.create_by_apply_delta(delta, new_revision_id,

                propagate_caches=propagate_caches)

            inv_lines = result.to_lines()

            return self._inventory_add_lines(new_revision_id, parents,

                inv_lines, check_content=False), result

        finally:

            basis_tree.unlock()

    def _iter_inventories(self, revision_ids):

        """Iterate over many inventory objects."""

        keys = [(revision_id,) for revision_id in revision_ids]

        stream = self.inventories.get_record_stream(keys, 'unordered', True)

        texts = {}

        for record in stream:

            if record.storage_kind != 'absent':

                texts[record.key] = record.get_bytes_as('fulltext')

            else:

                raise errors.NoSuchRevision(self, record.key)

        for key in keys:

            yield inventory.CHKInventory.deserialise(self.chk_bytes, texts[key], key)

    def _iter_inventory_xmls(self, revision_ids):

        # Without a native 'xml' inventory, this method doesn't make sense, so

        # make it raise to trap naughty direct users.

        raise NotImplementedError(self._iter_inventory_xmls)

    def _find_revision_outside_set(self, revision_ids):

        revision_set = frozenset(revision_ids)

        for revid in revision_ids:

            parent_ids = self.get_parent_map([revid]).get(revid, ())

            for parent in parent_ids:

                if parent in revision_set:

                    # Parent is not outside the set

                    continue

                if parent not in self.get_parent_map([parent]):

                    # Parent is a ghost

                    continue

                return parent

        return _mod_revision.NULL_REVISION

    def _find_file_keys_to_fetch(self, revision_ids, pb):

        rich_root = self.supports_rich_root()

        revision_outside_set = self._find_revision_outside_set(revision_ids)

        if revision_outside_set == _mod_revision.NULL_REVISION:

            uninteresting_root_keys = set()

        else:

            uninteresting_inv = self.get_inventory(revision_outside_set)

            uninteresting_root_keys = set([uninteresting_inv.id_to_entry.key()])

        interesting_root_keys = set()

        for idx, inv in enumerate(self.iter_inventories(revision_ids)):

            interesting_root_keys.add(inv.id_to_entry.key())

        revision_ids = frozenset(revision_ids)

        file_id_revisions = {}

        bytes_to_info = inventory.CHKInventory._bytes_to_utf8name_key

        for record, items in chk_map.iter_interesting_nodes(self.chk_bytes,

                    interesting_root_keys, uninteresting_root_keys,

                    pb=pb):

            # This is cheating a bit to use the last grabbed 'inv', but it

            # works

            for name, bytes in items:

                (name_utf8, file_id, revision_id) = bytes_to_info(bytes)